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71.
72.
A novel vanadium(V) phosphate and the arsenate analogue, [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))].H(2)O (X = P, As; bpy = bipyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are the first structurally characterized compounds in the vanadium(V)/4,4'-bpy/phosphate (or arsenate) systems. The two compounds are isostructural and crystallize in the triclinic space group P macro (No. 2) with a = 7.9063(3) A, b = 10.2201(4) A, c = 12.1336(5) A, alpha = 113.4652(7) degrees, beta = 95.7231(7) degrees, gamma = 94.4447(7) degrees, and Z = 2 for the phosphate, and a = 7.8843(6) A, b = 10.3686(7) A, c = 12.2606(9) A, alpha = 113.464(1) degrees, beta = 95.560(1) degrees, gamma = 94.585(1) degrees, and Z = 2 for the arsenate. The structure consists of phosphate-bridged vanadium(V) double chains linked through 4,4'-bpy ligands to form a sheet with the monoprotonated 4,4'-Hbpy(+) ligand being coordinated to the metal atom as a pendent group. The (1)H MAS NMR spectrum exhibits four resonances at 14.2, 9.5, 7.2, and 3.7 ppm with an intensity ratio close to 1:6:6:2, corresponding to three different types of protons in 4,4'-bpy and 4,4'-Hbpy(+) and one type of protons in H(2)O. The peak at 14.2 ppm can be assigned to the proton bonded to the pyridine nitrogen atom, which confirms the presence of 4,4'-Hbpy(+). 相似文献
73.
Kuang-Yu Hu Jia-An Wuu Ming-Ching Kao Yu-Tien Liu Shou-Hsiung Pai 《Applied biochemistry and biotechnology》1998,73(2-3):231-241
Streptomyces chusanensis ZS-2, isolated from a soil sample in Chusan in Taiwan, was found to produce a new Type II restriction endonuclease. This
restriction enzyme was designated as SchI. The purified enzyme was characterized as having a subunit mol wt of 28 kDa, and
was apparently free from exonuclease activities. It cleaves the phosphodiester bond between the fourth C and the fifth G on
the 5’-CCGCGG-3’ sequence of DNAs, leaving a 2-nucleotide protruding end at its 3’ site. This data suggests that SchI is an
isoschizomer of SacII. In addition, based on the comparison between SchI and SacII regarding reaction parameters, it seems
that SchI is a better choice of restriction enzyme for genetic analysis and mapping. 相似文献
74.
Yih-Shing Duh Jin-Min Yo Wen-Lian Lee Chen-Shan Kao Jing-Ming Hsu 《Journal of Thermal Analysis and Calorimetry》2014,116(1):339-347
Studies on the thermal decompositions of diamyl peroxide (DAPO), dicumyl peroxide (DCPO), and tert-butyl cumyl peroxide (TBCP) were conducted by DSC. Heat of decomposition, exothermic onset point, and chemical kinetics were determined and compared to those data of di-tert-butyl peroxide (DTBP), a model compound for studying thermokinetics of organic peroxide and standardization of a calorimeter. Similarities and differences of decomposition mechanisms between these organic peroxides were proposed and verified. Kinetics on decomposition of uni-molecular reaction via these similar alkoxyl radials accompanying β C–C bond scission were discussed and compared to the results from ab initio calculations. The ranking of thermal stability on dialkyl peroxides is determined to be in the following sequence: DCPO < TBCP < DAPO < DTBP. This rate-determining step in thermal decomposition of dialkyl peroxides possessed an average eigenvalue of log A at about 13.1 ± 1.2. Activation energy on the thermal decomposition of these peroxides was calculated to be 139.5 ± 14.4 kJ mol?1. 相似文献
75.
Wei-Jie Ou Chen-Shan Kao Yih-Shing Duh Jing-Ming Hsu 《Journal of Thermal Analysis and Calorimetry》2014,116(3):1111-1116
Thermal instability of lithiated cathode materials with organic carbonate were investigated using DSC. Lithium transition metal oxides of LiFePO4, LiMn2O4, and LiCoO2 were mixed with diethyl carbonate, dimethyl carbonate, ethylene carbonate, ethyl methyl carbonate, and propylene carbonate then dynamically screened to about 500 °C. Curves were acquired and analyzed to determine exothermic onset temperatures and reaction enthalpies. These data for assessing the thermal hazards of lithium-ion batteries under discharged conditions were compared to those data published in the literature. 相似文献
76.
77.
Weihong Qiu Tanping Li Luyuan Zhang Yi Yang Ya-Ting Kao Lijuan Wang Dongping Zhong 《Chemical physics》2008,350(1-3):154
Quenching of tryptophan fluorescence in proteins has been critical to the understanding of protein dynamics and enzyme reactions using tryptophan as a molecular optical probe. We report here our systematic examinations of potential quenching residues with more than 40 proteins. With site-directed mutation, we placed tryptophan to desired positions or altered its neighboring residues to screen quenching groups among 20 amino acid residues and of peptide backbones. With femtosecond resolution, we observed the ultrafast quenching dynamics within 100 ps and identified two ultrafast quenching groups, the carbonyl- and sulfur-containing residues. The former is glutamine and glutamate residues and the later is disulfide bond and cysteine residue. The quenching by the peptide-bond carbonyl group as well as other potential residues mostly occurs in longer than 100 ps. These ultrafast quenching dynamics occur at van der Waals distances through intraprotein electron transfer with high directionality. Following optimal molecular orbital overlap, electron jumps from the benzene ring of the indole moiety in a vertical orientation to the LUMO of acceptor quenching residues. Molecular dynamics simulations were invoked to elucidate various correlations of quenching dynamics with separation distances, relative orientations, local fluctuations and reaction heterogeneity. These unique ultrafast quenching pairs, as recently found to extensively occur in high-resolution protein structures, may have significant biological implications. 相似文献
78.
79.
80.
We reported the first syntheses of 2- and 3-(2-(benzo[b]selenophen-2-yl)-indoles and their Diels–Alder reactions to furnish six unique annulated benzoselenphene carbazoles. This facile route can be used to synthesize selenium-containing biindolyl derivatives that possessed potential pharmaceutical activities. 相似文献